Communication device with diversity antenna

ABSTRACT

A method and apparatus is disclosed for improving signal reception in a wireless communication device by selectively processing one of two or more signals received over two or more antennas that are configured at least partially orthogonal. In one embodiment, the signal source selection is based on comparison of a signal error rate to a threshold value. Error rates in excess of the threshold value may initiate a switching apparatus to selectively enable signal reception from a different antenna to improve the error rate. In one embodiment, amplifiers are located between the switching apparatus and the two or more antennas to thereby reduce noise. In an alternative embodiment control signals selectively enable and disable the amplifiers to control signal reception.

RELATED APPLICATIONS

This application is a continuation application of U.S. patentapplication Ser. No. 10/665,961 entitled “COMMUNICATION DEVICE WITHDIVERSITY ANTENNA”, filed on Sep. 18, 2003 and incorporated by referenceherein.

FIELD OF THE INVENTION

This invention relates generally to wireless communication and inparticular to a communication device having one or more antennas and amethod utilizing the one or more antennas.

BACKGROUND

Wireless devices are playing an increasingly significant role as acommunication tools throughout the world. Examples of wirelesscommunication devices include portable radios, cellular or wirelesstelephones, pagers, electronic messaging devices, and the like. As thecost of ownership of wireless communication devices has become moreaffordable, such devices have become a necessity for many people.

Today, there are over 123 million wireless mobile phone subscribers inthe United States alone. Because of the increased use and dependence ofwireless communications throughout the world, being able to communicateto others irrespective of one's location is of critical importance. Twofactors may affect a subscriber's ability to utilize wirelesscommunication network. First, the coverage of the network, which is afunction of the number of base stations and second, the ability of thesubscriber's wireless communication device to receive the signal.

One drawback of existing wireless communication devices is an inabilityto effectively receive an incoming voice or data signal. To achievereception, the incoming electromagnetic signal is picked up by anantenna, which is responsible for transmitting and receiving themodulated carrier signal that contains the desired signal (voice ordata) information. The wireless communication device's ability tocapture, demodulate, and decode the received signal will depend on anumber of factors, such as the signal strength and nearby signalobstructions.

For example, existing wireless communication devices may have difficultyreceiving a signal in the presence of tall structures, such as buildingsfound in metropolitan environments. In such environments, the originalsignal is often cluttered with replicas of the original signal that areweaker in amplitude. This often causes problems in reception as itbecomes difficult for the discriminator of the mobile communicationsdevice to detect the original signal.

Furthermore, there are changing environmental factors such asprecipitation and terrain that could affect the signal strength orcreate signal reflections, and hence affect the wireless communicationdevice's ability to receive the signal. In addition, dead spotsencountered in mountainous or wooded areas can block or weaken signalsand are a serious drawback to wireless communication.

The drawbacks mentioned above are factors which contribute to areduction of the signal to noise ratio (SNR) of a signal provided to atransceiver of the wireless communication device. This correlates to anincrease in a symbol or bit error rate of a demodulated baseband digitalsignal. When receiving voice information, these above-mentioneddrawbacks may result in a decrease in perceived speech quality. In thecase of data, the net result may be significant packet loss due to biterrors. As a result, there exists a need for a method and apparatus tomore effectively capture and process the signal at the wireless mobilecommunication device.

As discussed above, communication devices based on prior art designs maysuffer from poor reception when presented with signal receptionchallenges. The method and apparatus described herein overcomes thedrawbacks of the prior art by introducing two or more antennas havingdifferent signal reception properties or capabilities into a wirelesscommunication device. In one embodiment the antennas are configured atleast partially orthogonal to each other to thereby improve signalreception. Selection as to which antenna's signal to utilize as thereceived signal may be based on signal analysis. For example, duringdevice operation, a processor or other control device may calculate theerror rate of the incoming signal and compare the error rate to athreshold value. Based on the comparison between the error rate and athreshold value, the system may process a signal from a differentantenna.

In one embodiment a control signal modifies a switch setting toselectively provide a signal, selected from two or more signals receivedover the two or more antennas, to the processing apparatus of thecommunication device. A processor or other control system may generatethe control signals.

One or more control algorithms may be enabled to refine the signalselection process to reduce or eliminate hunting between antennas. Onepotential algorithm implements a time delay between switching events.Other algorithms may require that after a switching event the error ratemust surpass a second threshold value before another switching eventwill occur. It is contemplated that multiple threshold values may existdepending on previous signal selection and error rate history.

In one embodiment an amplifier is located prior to the switching deviceto reduce the impact of passing the signal through the switching device.By amplifying the signal prior to switching, the degradation in thesignal to noise ratio resulting from the switching device is reduced.Thus, any additional noise introduced by the switch is reduced.

It is further contemplated that the amplifiers may be selectivelyenabled or disabled to control which antenna's output is provided to thecommunication device processing system. In such an embodiment, thedrawbacks associated with a switching device are eliminated.

The method and apparatus described herein possess numerous advantagesover the prior art. One such advantage is improved signal reception. Ininstances when the signal is weak, reflected, or received in a mannermaking reception by the antenna difficult, the dual and partiallyorthogonal antenna arrangement provides improved reception. Anotheradvantage is an improved signal to noise ratio in embodiments thateliminate the switching device. Alternatively, the switching device maybe located, in relation to an amplifier, in a manner that minimizesnoise.

Other systems, methods, features and advantages of the invention will beor will become apparent to one with skill in the art upon examination ofthe following figures and detailed description. It is intended that allsuch additional systems, methods, features and advantages be includedwithin this description, be within the scope of the invention, and beprotected by the accompanying claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingfigures. The components in the figures are not necessarily to scale,emphasis instead being placed upon illustrating the principles of theinvention.

FIG. 1 illustrates a block diagram of a wireless communication device.

FIG. 2 illustrates a block diagram of an example embodiment of theinvention.

FIG. 3 illustrates a detailed block diagram of an example embodiment ofan example implementation of the invention.

FIG. 4 illustrates an operational flow diagram of an example method ofsignal selection.

FIG. 5 illustrates a block diagram of an alternative embodiment having aswitching element.

FIG. 6 illustrates a block diagram of an alternative embodiment having aresistive network.

FIG. 7 illustrates a block diagram of an alternative embodiment having aswitching element located on an antenna side of an amplifier.

FIG. 8 illustrates a block diagram of an alternative embodiment having aswitching element located an antenna side of a duplexer.

DETAILED DESCRIPTION

A method and apparatus is provided for providing a more robust signal toa receiver in a wireless communication device. The method and apparatusmay be implemented in a wide variety of wireless environments, such aswireless telephones, base stations, radios, desktop computers, intercomsystems, surveillance systems, alarm systems, mobile messaging devices,pagers, personal digital assistants, and the like. In the followingdescription, numerous specific details are set forth in order to providea more thorough description of the present invention. It will beapparent, however, to one skilled in the alt, that the present inventionmay be practiced without these specific details. In other instances,well-known features have not been described in detail so as not toobscure the invention.

FIG. 1 illustrates a block diagram of an example environment for use ofthe method and apparatus described herein. This is but one exampleenvironment and it is contemplated that other environments of use wouldbenefit from the principles of the invention. The example environmentshown in FIG. 1 comprises a wireless communication device 104. Thewireless communication device 104 comprises a first antenna 108 and asecond antenna 112 configured to receive a wireless signal. In oneembodiment the antennas 108, 112 receive a carrier signal with voice ordata information modulated or coded within the carrier signal. Examplesof wireless mobile communication devices include cellular/PCStelephones, pagers, electronic messaging/e-mail devices, wirelessPersonal Digital Assistants (PDA), wireless Internet appliances, and thelike.

The antennas 108, 112 are connected to RF front-end circuitry 116 asshown in FIG. 1. In one embodiment, the first antenna 108 comprises awhip antenna and the second antenna 112 comprises an internal antennanot visible to the user of the wireless communication device. Theantennas 108, 112 may comprise any component that is capable ofcollecting or radiating electromagnetic waves from the environment. Theantennas 108, 112 may be designed to operate over a particular range offrequencies. The size and shape of the antennas 108, 112 may dictateit's frequency, rain, and radiation and reception characteristics.Examples of different antennae include whip, omni, dipole, cornerreflector, horn, helix, patch, Yagi, parabolic dish, and panel.

A transceiver 120 connects to the RF front end circuitry 116. Thetransceiver 120 detects, processes, and filters a carrier wave togenerate a signal that can be further processed by processor circuitry128. In addition, the transceiver 120 may perform the reverse functionwhen in transmit mode by modulating a source signal to an appropriatecarrier wave frequency and transmitting the modulated signal through theRF front-end circuitry 116 and the antenna. The transceiver 120 maycomprise a modulator, demodulator, frequency synthesizers, filters, andother devices or systems designed to receive and transmit signals.

The processor 124 connects to the transceiver 120, a display 128, amemory 132, and a user interface 136. The processor 124 comprises one ormore integrated circuits that functions as the central processing unitof the wireless communications device 104. The processor 124 functionsmay comprise baseband digital signal processing, voicecompression/decompression, speech synthesis of the data stream, and thegeneration of control signals to the RF front-end circuitry. Otherfunctions of the processor 124 comprise supporting the display 128, theuser interface 136, and the memory 132.

The display 128 provides visual information to the user of the wirelesscommunication device. The display 128 may provide information to theuser regarding the current status of the wireless communication device.In one embodiment, the display comprises a liquid crystal display (LCD).In another embodiment, the display comprises light emitting diodes(LED). It is contemplated that the display 128 could also comprise anactive or passive matrix display. The display 128 may electricallycommunicate to a device that emits audible signals to alert the user ofan event.

The memory 132 may comprise a flash memory, random access memory, readonly memory, or a hard disk drive (such as a micro-drive). The memory132 may contain data configured by the manufacturer or contain data thatis input by the user, such as data that is specific to the user of thewireless communications device. For example, the memory 132 provides theflexibility to expand a wireless communication device's features withservices such as storage of a user's phone directories, preferredroaming codes, voicemail, or other information.

The user interface 136 comprises a device that allows the user to inputdata into the wireless communications device 104. This data may be usedto control the operation of the wireless mobile communication device104. A possible embodiment of the fuser interface 136 is a tactilekeypad. It is contemplated that in another embodiment, the userinterface 136 comprises a voice recognition system.

The power source 140 provides power to the electronic components of thewireless communication device 104. The power source 140 may obtain powerthrough an input power jack 144. The power source 140 may comprise adisposable or a rechargeable energy storage device such as for example abattery. In the event the power source 140 is rechargeable, the powersource may be charged through the use of the power jack 144. In otherembodiments, it is contemplated that the power source 140 may be chargedthrough solar cells. The power jack 144 comprises a connector fordelivering power from an external source. Examples of external sourcesinclude independent power supplies, voltage sources from a wall jack,automobile DC adapters, and the like.

FIG. 2 is a block diagram of an example embodiment of the invention. Ingeneral, the method and apparatus disclosed herein provides a diversityantenna approach to the signal reception including an amplifier locatedbetween an antenna and the two or more antennas. As a result of thediversity antenna approach, signal reception is improved over single ornon-diverse multiple antenna systems. Location of the amplifier prior tothe switching element provides the advantage of a better signal to noiseratio (SNR) than compared to the systems prior art.

As shown in FIG. 2, a first antenna 204 connects to the input of a lownoise amplifier 208. The output of the low noise amplifier 208 connectsto a switch 212. The low noise amplifier 208 receives the signal outputfrom the antenna 204 and amplifies the signal to a suitable power levelfor transmission to the switch 212. A second antenna 216 connects to theinput of a low noise amplifier 220. The output of the low noiseamplifier 220 connects to the input of the switch 212. The switch 212connects to a transceiver 228, which in turn connects to a controller224.

The switch 212 is controlled by the controller 224 to provide the signalreceived from the first antenna 204 or the second antenna 216 to thetransceiver 228. At the transceiver 228 the signal is processed anddemodulated to baseband. The transceiver 228 may output the demodulatedbaseband signal into the controller 224 or the controller may simply tapinto the transceiver. Either the transceiver 228 or the controller 224may analyze the signal to determine a signal to noise ratio, a bit errorrate or a symbol error rate. As a result of this error analysis, thecontroller 224 may output control signal(s) to the switch 212. Inresponse to the control signals, the switch 212 may select the outputfrom either antenna 204, 216 to couple to the transceiver 228.

It is contemplated that various switch control algorithms may be adoptedto determine switch decisions. In one embodiment the error rate ismonitored on an ongoing basis. As the error rate reaches a threshold oris maintained above an undesirable level for a sufficient period oftime, the controller 224 may toggle the switch 212 via a control signal.The threshold need not be a fixed number. Depending on the algorithm,the threshold may be made adaptive to better match the radio propagationenvironment. The portion of the transceiver 228 responsible forreceiving the signal and the controller 224 may be collectively referredto as the receiver. The controller 224 and transceiver are shown asseparate elements for purposes of discussion. It is fully contemplatedthat the controller 224 and transceiver 228 functions may be combinedinto a single device.

Antenna 204, 216 can be designed, spatially positioned, or configured tobe orthogonal or partially orthogonal to each other. As an example, thetwo antenna 204, 216 may be orthogonally polarized. When antennas areorthogonal or partially orthogonal, a received signal may be moreeffectively captured by one of the antennas than the other. This mayoccur when the correlation of an electromagnetic field directionalvector of the received signal with a directional vector associated withthe polarization plane of the first antenna 204 is greater than theresult from correlation to the second antenna 216. Overall, theinclusion of an additional antenna 216 provides a “diversity” approachto improving the reception of an electromagnetic wave by providing analternate signal source. Although shown with two antennas, it iscontemplated that more than two antennas may be utilized to furtherimprove reception.

As a further advantages to the system shown in FIG. 2, the signal isamplified by the low noise amplifiers 20, 220 prior to passing throughthe switch 212. There is an advantage associated with amplifying thesignal prior to switching in that the magnitude of the signal, inrelation to noise, presented to the transceiver 228 is greater when thesignal is amplified prior to switching because the attenuationintroduced by the switch is a lower percentage of the total signalmagnitude. In contrast, when the switching occurs prior toamplification, the noise levels associated with the signal areincreased. As a result, amplifying the signal prior to executing aswitching operation results in better reception properties for thewireless communication device.

This relationship is illustrated by the following equation:

N=KT_(c)B

where N represents the noise introduced by an element or group ofelements, k represents Boltzmann's constant i.e. ˜1.38×10⁻²³, T_(c)represents a composite noise temperature and B represents an effectivebandwidth. The composite noise temperature is based on the contributionof noise by the combination of a lossy component and an amplifier. HenceT_(c) may be expanded as:

T _(c) =T _(amp) +T _(swch)

such that T_(amp) represents the composite noise of the amplifier andT_(swch) represents the composite noise of the switch.

To illustrate the benefits of one aspect of the method and apparatusdescribe herein, two different switch and amplifier configuration areanalyzed. In a first configuration and as contemplated herein, thesignal is first amplified and then fed into a switching element. Thecomposite noise of the arrangement may be represented as above, suchthat:

T _(c) =T _(amp) +T _(swch)

where T_(amp) represents the composite noise of the amplifier andT_(swch) represents the composite noise of the switch. In a secondconfiguration, the signal first passes through a switching element andis thereafter amplified. The composite noise of the arrangement may berepresented as above, such that:

T _(c) =T _(swch) [L _(swch) ×T _(amp)]

such that T_(amp) represents the composite noise of the amplifier,T_(swch) represents the composite noise of the switch, and L representsa value greater than one that is associated with noise introduced by theswitch. As can be appreciated, the resulting noise introduced into thesignal is less when the signal is first amplified and then switched.

FIG. 3 comprises an example implementation of one embodiment of themethod and apparatus described herein. In general, FIG. 3 illustrates afirst antenna 336 and a second antenna 332 connected to a RF front-endcircuitry 376. The RF front-end circuitry 376 communicates withprocessor circuitry 372 and a transceiver 320. These apparatus aredescribed below in greater detail.

The first antenna 332 may comprise an external antenna typical to awireless mobile communication device while a second antenna 336 maycomprises an additional small internal antenna within the wirelesscommunication device. The first antenna 332 connects to the input of aduplexer 368. The first antenna 332 receives the carrier signal that issubsequently provided to a duplexer 336. The duplexer 368 is a devicethat uses tuned circuits to isolate the transmitted frequencies from thereceived frequencies. The duplexer 368 isolates the received signal andthen sends it to the low noise amplifier 328. The low noise amplifier328 amplifies the received signal to an appropriate voltage. The outputof the low noise amplifier 328 connects to a signal node 360.

The second antenna 336, provides an additional device receiving for thesignal. The second antenna 336 may be configured to be orthogonal to thefirst antenna 332. As a result, the embodiment as shown in FIG. 3provides an alternate path for the received signal to reach thetransceiver 320. The output of the second antenna 336 connects to theinput of a filter 344. The filter is configured to selectively acceptonly the frequency band of interest. The filter output connects to a lownoise amplifier 324 which is configured to amplify the received signalto an appropriate voltage. The output of the low noise amplifier 324connects to the signal node 360.

A filter 340 is connected to the signal node 360 to receive and filterthe output of the amplifiers 324, 328. The output of the fitter 340feeds into a transceiver 320. The transceiver 320 comprises a deviceconfigured to process a signal upon reception and prior to transmission.The transceiver 320 connects to the filter 340, processing circuitry372, and a transmit path. Regarding the transmit path of the RFfront-end 376, the transceiver 320 connects to a filter 348 which inturn connects to a power amplifier 364.

In operation, the transmitter aspects of the transceiver 320, outputsthe transmitted signal to the filter 348. The filter 348 rejects certainfrequency bands and in turn passes a filtered signal to a amplifier 364.The amplifier 364 adjusts the signal to an appropriate voltage level fortransmission. The output of the amplifier 364 connects to the duplexer368, which functions as described above. The duplexer 368 provides thesignal to the first antenna 332. The filters 340, 344, 348 remove theunwanted frequencies outside of each filters' passband, thereby reducingthe noise component of the received signal.

In the embodiment shown in FIG. 3, processor circuitry 372 is includedto perform analysis on the received signal and, based on the analysis,control operation of the amplifiers 324, 328. In reference to theprocessor circuitry 372, a first processor 304 connects to a register316, a processor memory 312, and a second processor 308. In oneembodiment the first processor 304 is configured to analyze the signalto determine the signal quality or other parameter of the receivedsignal. It is contemplated that any parameter regarding the receivedsignal may be analyzed, including but not limited to a bit error rate, asymbol error rate and a signal to noise ratio The register 316 may beconfigured to store prior error rates or error values or a thresholdvalue. The processor memory 312 may contain software code comprising analgorithm, which is described in more detail below. The second processor308 may be configured to generate and output control signal to the lownoise amplifiers 324, 328 located in an RF front end circuitry 376. Theprocessors 304, 308 may comprise any type processor, control logic, DSP,ASIC, ARM or other device capable of determining an incoming signal'serror rate and selecting between two or more received signals tominimize an error rate.

In operation, the processor circuitry 372 is configured to provideeither the signal received from the first antenna 332 or the signalreceived from the second antenna 336 to the transceiver 320 bycontrolling the amplifiers. The first processor 304 analyzes the signalreceived from the transceiver 320 and make a determination regarding thequality of the signal. Responsive to control signals generated by thesecond processor 308 and provided via conductors 352 and 356, theamplifiers 324, 328 amplify either the signal received by the firstantenna 332 or the signal received by the second antenna 336. In oneembodiment the control signals on conductors 352, 356 selectivelydisable one of the low noise amplifiers while concurrently enabling theother amplifier. For example, if the control signal on conductor 352 isdisabling operation of amplifier 324, then the control signal onconductor 356 may be concurrently enabling amplifier 328. As a result,the signal from the second antenna 336 is no longer provided to thetransceiver 320 while the signal from the first antenna 336 becomes theprimary signal. It is contemplated that a signal selection algorithm orother control routine is responsible for the decision process. In oneembodiment, the algorithm is embodied in machine readable code, such assoftware code, and is stored in the processor memory 312 of theprocessor circuitry 372.

In one embodiment, the signal selection algorithm measures the signalquality such as the symbol error rate (SER) or data error rate of thereceived signal such as by analyzing the signal delivered by thetransceiver 320 to the processor circuitry 372. The transceiver 320 mayinterface with the first processor 304 as illustrated above. It iscontemplated that this algorithm can be programmed into the processormemory 312 enabled in hardware.

In another embodiment the signal selection algorithm tracks the trend ofthe current signal to determine if it is increasing or decreasing instrength. If the trend indicates a decreasing signal strength and it isapproaching the unacceptable threshold, then the algorithm would likelyswitch to the alternate rx path.

The following discussion represents one possible exemplary method ofoperation of the signal selection algorithm. When the wirelesscommunication device is first turned on, the device can be programmed tocommence reception via either of the first antenna 332 or via the secondantenna 336. When initial operation commences with the first antenna332, the received signal travels through a first conductive path, i.e.,a first path, defined by the two endpoint elements—the antenna 332 andthe node 360. Similarly, a second conductive path, can be defined by thetwo endpoint elements—the second antenna 336 and the node 360.

When a particular signal quality parameter, such as the symbol errorrate (SER), rises above a specified threshold defined as the variableTHR1, the processor circuitry 372, by way of the control signals carriedon conductors 352, 356, may initiate a transition whereby the signal isreceived from the second conductive path instead of the first conductivepath. If the SER does not exceed the threshold THR1, then receptioncontinues through the first conductive path, i.e. the first antenna 332.

In one embodiment the signal selection algorithm may have an additionalvariable, such as a time duration, T, during which the SER is monitored.If the SER is within an undesirable range SER>THR1 for a time durationgreater than time duration T, then a signal from an alternative path maybe selected for use. For example, the signal selection algorithm maytransition to a different signal when the SER exceeds the value THR1 forat least T seconds. Stated another way, transition occurs when SER>THR1and the time duration of SER>THR1 is greater than time T. It iscontemplated that based on these principles, one of ordinary skill inthe art will understand that other methods of operation are possible.

In the case where reception initially occurs via the internal antenna336, the SER of the received, signal may also trigger a similartransition. When the SER rises above a specified threshold THR2, theprocessor circuitry 372, by way of the control signals 352, 356, mayinitiate a transition to receive the signal via a different antenna. Thesignal selection algorithm may have as a variable, such as a duration oftime, T2, in which the SER is within an undesirable range (SER>THR2).For example, the algorithm may perform this transition when the SERexceeds the value THR2 for at least a time period T2. It should be notedthat THR1 and THR2 may be equal or different in value and T1 and T2 maybe equal of different in value.

In the embodiment pictured in FIG. 3, it is contemplated the transitionfrom the first antenna 332 path to the second antenna 336 path andvice-versa, occurs in a gradual fashion to reduce transient voltagesthat could affect the electrical performance of the circuitry or inducean excessive phase step in the signal which result in a demodulationerror. It is contemplated that this gradual transition occurs by slowlyvarying the amplitude of the voltages of the control signals onconductors 352, 356. In one embodiment the control signals on conductors352, 356 are tied to the appropriate voltage supply inputs throughadditional circuitry (such as buffer drivers) to the low noiseamplifiers 324, 328. By gradually increasing one of the supply voltages,over a period of typically a few milliseconds, while decreasing theother, it is contemplated that one of the low noise amplifiers 324, 328is gradually turned on while the other low noise amplifier 324, 328 isgradually turned off. As illustrated in FIG. 3, the outputs of the lownoise amplifiers 324, 328 are tied to the node 360. Hence, as one lownoise amplifier 324 328 turns off the output of this amplifier willappear to be an open circuit, allowing the other low noise amplifier toprovide a received signal to the input of the transceiver 320.

It is desired that the transitioning of the supply voltages isaccomplished in a gradual manner such that the input to the transceiver320 and the surrounding circuitry is unaffected by any transient voltagespikes. The overall result of this method and apparatus enables thewireless communication device to receive the desired signal from analternate path originating from an orthogonally configured antenna 332,336 in an effort in increase the quality of the received signal withoutinterfacing with signal reception.

FIG. 3 also offers the added benefit in that the signal loss associatedwith filter 344 is typically less than the receive path loss associatedwith duplexer 368. This means that the auxiliary receive path fromantenna 336 will have a performance advantage in its own right. Therebyimproving receive performance still further.

FIG. 4 illustrates an operational flow diagram of an example method ofoperation. It should be understood that this is one of several methodsof operation that may be implemented for the apparatus described hereinand that variations of the described algorithm can be implementedwithout departing from the scope of the claims that follow. At a step404, a first antenna receives a wireless signal. Any type signal may bereceived. Thereafter, at a step 408, the front-end circuitry filters andamplifies the signal. Various types of amplification or filtering mayoccur depending on the particular configuration of the wirelesscommunication device and the frequency band in which the signal ofinterest is located.

Next, at a step 412, a switch or other signal control device directs thesignal from the first antenna through to the receiver circuitry. In oneembodiment the receiver circuitry comprises a transceiver with anassociated processor. As an advantage of the method and apparatusdescribed, the received signal is amplified prior to passing through aswitch. As a signal pass through a switch it is attenuated, amplifyingthe signal prior to passage through a switch achieves a better signal tonoise ratio than if tie amplification occurs after the signal passesthrough a switch.

At a step 416, the signal is directed to processor circuitry where aparticular signal quality parameter, such as SER, can be determined. Inother embodiments a bit error rate (BER) or any other error rate orsignal reception parameter may be determined. Any manner of errorcalculation or error representation is contemplated.

In one embodiment, the processor circuitry compares the error rate, suchas an SER, to a threshold and then applies a signal selection algorithm.The following discussion represents one possible exemplary algorithm.The threshold at which a transition from the first antenna will occurmay be represented as a value THR1. In this configuration, the processorcircuitry samples the signal over time and calculates a running average,defined as SER_(avg) over a specified time period, T1, which commencesat the instant the SER falls above THR1. If the average symbol errorrate SER_(avg) over the time interval T1 is less than or equal to THR1,the system continues reception via the first antenna. Accordingly, if atstep 420, the SER_(avg) is less than or equal to SER1 over the timeinterval T1., then the operation returns to step 404 and operationcontinues in the manner described above.

Alternatively, if at step 420 the average error over time is greaterthan THR1, the operation advances to step 424 wherein processorcircuitry controls a switch or other switching device to enablereception from the second antenna. Any type switch or switching devicemay be utilized as described herein to control whether the signalreceived from a first antenna or a second antenna is provided to thetransceiver. In addition it is contemplated that more than two antennasmay be utilized to further improve signal reception capability.

Thereafter, at a step 428, the operation receives the signal via thesecond antenna and at a step 432 amplifies the signal received from thesecond antenna. Next, at a step 436, the amplified signal received viathe second antenna is directed through the switch to the receiver(receive portion of transceiver) circuitry. At the receiver circuitry,the error rate is determined. This occurs at a step 440. Any manner oferror calculation or error representation is contemplated. In oneembodiment, the processor circuitry computes the error rate, such as anSER and comparers the error rate, to a threshold. The threshold valuesutilized when receiving from the second antenna may be identical to ordiffer from the threshold utilized for reception with the first antenna.For purposes of discussion, the threshold utilized when receiving withthe second antenna is defined as THR2. As defined in step 440—theprocessor circuitry may sample the signal over time and calculate anaverage SER (SER_(avg)) over a period of time, T2, which commences ifthe SER rises above THR2.

If the average symbol error rate (SER_(avg)) over the time interval T2is less than or equal to SER2, the system continues reception via thesecond antenna. Accordingly, if at step 444, the SER_(avg) is less thanor equal to SER2 over the time interval T2, then the operation returnsto step 428 and the operation continues in the manner described above.

It is contemplated that this method calculates an average error rate,i.e. an error rate over a specified period of time, before a comparisonis made to a specific threshold. As T1 or T2 increases, this algorithmprovides the advantage of reducing a momentary change in error rate frominitiating a switching operation. This eliminates hunting betweenantennas for a desired signal in the event neither antenna will yield asignal having a SER below the threshold.

It is further contemplated that the signal selection algorithm maymeasure the percentage of samples that fall within a specified rangesabove the threshold. These percentage values can also be used as adecision variable to control switching. For example, the percentage ofsamples that falls above the threshold may be tabulated over a specifiedperiod of time.

Another embodiment, shown in FIG. 5, is similar to that of FIG. 3, butemploys a switch 504, instead of a signal node, connected to the outputof the low noise amplifiers 324, 328. With regarding to FIG. 3 and FIG.5, similar elements are identified with identical reference numerals.The switch 504 comprises circuitry responsive to the control signalsprovided via conductors 352, 356 from from the processor circuitry 520.In this embodiment, it is contemplated the switch 504 provides acontrolled mechanism to switch an output of the low noise amplifiers324, 328 to the input of the filter 340. Although the control signals onconductors 352, 356 may provide adequate control of the outputs of thelow noise amplifiers 324, 328, the use of the switch 504 may provide anadded degree of control when the system selects the output of one lownoise amplifier to the other. The switch 504 may comprise any electricalelement capable of achieving or controlling connections between theinput to the filter 340 and either the output of the low noise amplifier324 or the output of the low noise amplifier 328. While the switch mayintroduce some amount of signal attenuation there is an added degree ofcontrol. In an alternative embodiment, the control lines 352, 356 areeliminated and the switch 504 is solely responsible for determining thesignal provided to the transceiver 320.

FIG. 6 illustrates a block diagram of an alternative embodiment of theinvention. FIG. 6 shares numerous similarities with FIG. 3 and, as aresult, similar elements are identified with identical referencenumerals. In this instance, the switch 504 described in FIG. 5, isreplaced by a resistive network 604. In one example embodiment theresistive network 604 comprises three resistors 606, 608, 612, whichconnect the outputs of the low noise amplifiers 324, 328 to the input ofthe transceiver 320 via the filter 340. The low noise amplifiers 324,328 in conjunction with the control signals on conductors 352, 356operate as described previously in the text associated with FIG. 5. Thevalues of the three resistors 606, 608, 612 are selected to maximize theSNR at the input of the transceiver 320. It is contemplated thatresistive networks other than that shown may be used. Moreover,components other than resistors may be added to achieve desiredoperation.

FIGS. 7 and 8 illustrate block diagrams of alternative embodiments ofreceiver systems with dual antennas such that the received signal isprocessed by an antenna switching element, switching system, orswitching device prior to processing by the low noise amplifiers. FIG. 7illustrates a block diagram of an alternative embodiment configured withan amplifier 712 located after an antenna selector switch 704. Portionsof FIG. 7 are identical to portions of FIG. 3 and accordingly identicalelements are referenced with identical reference numerals. The followingdiscussion applies to the portions of FIG. 7 that differ from aspectsdescribed above. Collectively, the elements inside the dashed linecomprise the RF front-end circuitry 376. As shown, the antenna 332connects to the duplexer 368, which in turn connects to the amplifier364 as described above. The amplifier 364 connects to the filter 348,which in turn connects to the transceiver 320.

The duplexer 368 also connects to a switch 704. The switch 704 receivessignals from the filter 344 via the second antenna 336. In thisembodiment, the output of the switch 704 connects to a low noiseamplifier 712. In contrast to previous embodiments, the switch 704 islocated on the antenna side of the amplifier 712. As in previousembodiments, the switch 704 receives control input from the processorcircuitry 372, in this embodiment, via conductor 708. The low noiseamplifier 712 amplifies the signal to an acceptable level and outputsthe amplified signal to the filter 340, which in turn delivers thereceived signal to the transceiver 320.

In operation, the processor circuitry 372 analyzes an error rate of thereceived signal. The processor circuitry 372 may calculate the errorrate or the transceiver 320 may provide the error rate to the processorcircuitry. The processor circuitry 372 responds to the error rate byproviding a control signal to the switch 704. The control signalprovided via conductor 708 to the switch 704 forces the switch todirect: a signal from either the first antenna 332 or second antenna 336to the transceiver 320. The switch 704 is functionally similar to theswitch 504 described earlier in FIG. 5. The switch 704 may comprise anyelectrical element capable of controlling the connection between theinput of low noise amplifier 712 to either the output of the filter 344or the output of the duplexer 368. The algorithm applied by theprocessor circuitry 372 may be generally similar to that describedpreviously in conjunction with FIG. 4. As an advantage to theconfiguration shown in FIG. 7, only a single amplifier 712 is required.This may reduce the cost, size, and power consumption of the devicewhile still providing the advantage of a dual antenna approach.

FIG. 8 illustrates a block diagram of an alternative embodimentconfigured with an antenna switching element 804 located between the twoor more antennas 832, 836 and a duplexer 368. Portions of FIG. 8 areidentical to FIG. 3 and accordingly, identical elements are referencedwith identical reference numerals. The following discussion applies tothe portions of FIG. 8 that differ from aspects described above.Collectively, the elements inside the dashed line comprise the RFfront-end circuitry 376. Antennas 832, 836 connect to the switch 804 asshown. It is contemplated that the antennas 832, 836 are configured tobe at least partially orthogonal to gain the benefits of differentreception characteristics. The switch 804 may comprise any electricalelement capable of connecting the input of the duplexer 368 to eitherthe output of the antenna 832 or the output of the antenna 836.

As in previous embodiments, the switch 804 receives control input fromthe processor circuitry 372, in this embodiment, via conductor 808. Theoutput from the switch feeds into the duplexer 368. The duplexer 368isolates the received signal and transmits it to the low noise amplifier328. The signal is amplified and forwarded to the filter 340 whereunwanted frequency components are removed. The filter 340 outputs thesignal to the transceiver 320 for further processing as described above.

In operation, the processor circuitry 372 determines an error rate ofthe received signal that is generated by the transceiver 320. Theprocessor circuitry 372 responds to the error rate by providing acontrol signal to the switch 804. The control signal provided viaconductor 808 to the switch 804 selects the received signal from eitherantenna 832 or antenna 836. The switch 804 may be functionally similarto the switches described earlier. The switch selection algorithmapplied by the processor circuitry 372 may be similar to that describedpreviously in FIG. 4.

As an advantage of the embodiment illustrated in FIG. 7 the filter 344(FIG. 7) is eliminated. This may reduce the cost and size of the unit.Furthermore, the embodiments described herein reduce the error rateassociated with a received signal by selecting one of two or moresignals for processing. To reduce power consumption, active devices inthe signal path and not in use may be powered down by control signalsgenerated from the processor circuitry 372.

While various embodiments of the invention have been described, it willbe apparent to those of ordinary skill in the art that many moreembodiments and implementations are possible that are within the scopeof this invention. It is contemplated that the, invention can beimplemented in a plurality of other environments, such as anyenvironment where an improvement in the received SNR might providebenefit in the operation of a wireless communication device. Further, itwill be understood that the above described arrangements of apparatusand the methods there from are merely illustrative of applications ofthe principles of this invention and many other apparatus and methodsmay be implemented without departing from the sprit and scope of theinvention as defined in the claims.

1. A system to reduce a data error rate associated with a signalreceived by a wireless communication device comprising: a first antennaconfigured to receive a signal; a second antenna configured to receivethe signal, the second antenna configured at least partially orthogonalto the first antenna; a processor configured to determine an error rateassociated with the signal and generate one or more control signals; anda switching element, responsive to the one or more control signals,configured to selectively provide either the signal received via thefirst antenna or the signal received via the second antenna to theprocessor; wherein the switching element comprises a first amplifier anda second amplifier, and wherein operation of the first amplifier and thesecond amplifier is controlled by the one or more control signals. 2.The system of claim 1, wherein the one or more control signals isgenerated in response to the error rate exceeding a threshold.
 3. Amethod of switching between a signal received over a first antenna or asecond antenna by switching between the first antenna and the secondantenna comprising: receiving a signal with a first antenna; determiningan error rate of the signal; comparing the error rate of the signal to athreshold; generating a control signal, responsive to the comparing,wherein the control signal determines whether the signal provided to areceiver is received over the first antenna or the second antenna;providing the signal received over the first antenna or the secondantenna to the receiver based on the control signal; and furthercomprising providing the control signal to one or more amplifiers,wherein the control signal controls a level of amplification of thesignal received over the first antenna and the second antenna.
 4. Themethod of claim 3, filter comprising: slowly decreasing theamplification of a first amplifier coupled to the first antenna; whilesimultaneously, slowly increasing the amplification of a secondamplifier coupled to the second antenna.
 5. A method of receiving asignal comprising: receiving a signal with a first antenna; receivingthe signal with a second antenna, responsive to one or more controlsignals from a processor; amplifying either the signal received from thefirst antenna or the signal received from the second antenna to createan amplified signal; directing the amplified signal to a processor;analyzing the amplified signal with the processor to determine an errorrate associated with the amplified signal; comparing the error rate to athreshold value; and generating one or more control signals to controlthe amplifying if the comparing reveals that the error rate is greaterthan the threshold value.
 6. The method of claim 5, wherein comparingthe error rate of the amplified signal to a threshold value comprisescomparing an average error rate of the amplified signal to a thresholdvalue.
 7. The method of claim 5, wherein the threshold value comprises amaximum error rate value, such that error rates greater than thethreshold value result in the processor generating a control signal toamplify the signal received from an alternate antenna.
 8. The method ofclaim 5, further comprising providing the control signal to a switch,wherein the switch is configured to direct either the signal from thefirst antenna or the second antenna to the processor.
 9. The method ofclaim 5, wherein the first antenna is at least partially orthogonal tothe second antenna.
 10. An apparatus for switching between a first inputand a second input within a wireless communication device configured toreceived a signal comprising: a first conductive path having a firstamplifier and first output; a second conductive path having a secondamplifier and second output, wherein the first output and the secondoutput are connected to a node; and a processor configured to receive asignal from the node and present control signals to the first amplifierand the second amplifier, wherein said control signals selectivelyenable or disable the first amplifier and the second amplifier.
 11. Theapparatus of claim 10, wherein the node comprises a resistive network.12. The apparatus of claim 10, wherein the node comprises a switch. 13.The apparatus of claim 10, wherein the first conductive path connects toa first antenna and the second conductive path connects to the secondantenna and the first antenna is at least partially orthogonal to thesecond antenna.
 14. The apparatus of claim 10, wherein the firstamplifier and the second amplifier amplify the signal prior to thesignal arriving at the node.